The invention relates to a method of heating multifractional materials and an apparatus for implementing the same.
The invention is particularly adapted for use in the production of blast furnace coke briquettes. One critical stage in the production of blast furnace coke from low-caking coal consists in heating coal, which is a multi-fractional material, to a temperature sufficient to cause coal grains to become plastic before briquetting.
There is known in the prior art a method of heating multi-fractional materials, e.g. coal, in a stream of heat carrier gas, in which multi-fractional materials enter in a step-by-step fashion the stream of heat carrier during the process of progressive heating, the stream having a zone of maximum temperature and a plurality of zones of relatively low temperature. Multi-fractional materials are introduced into the stream of heat carrier in such a manner that they are first heat-treated in the zone of relatively low temperature, ending up in the maximum-temperature zone.
An apparatus known in the prior art is also an apparatus for carrying the above method into effect, which includes a means for producing a heat carrier, and heater units having feed tubes for supplying multi-fractional materials and a heat carrier, a means adapted to separate the materials from waste heat carrier, a tube for discharge of heat carrier and tube for discharge of heated materials, both connected to the separating means.
The old method and apparatus for its implementation suffer from the disadvantages of an inefficient distribution of heat during the process in the various temperature zones of the stream, from the inability to control the stream, and the consequent limited efficiency of the apparatus, and from the fact that the materials tend to be heated in a non-uniform manner depending on their particle size.
There is also known in the prior art a method of heating loose multi-fractional materials, in which after passing through each temperature zone of the heat carrier the materials are subjected to isothermal conditions for the purpose of equalizing the temperatures of various fractions thereof.
The method referred to above does not provide the versatility enough to regulate the heat distribution as between the various temperature zones of the stream, nor is it effective to prevent the smaller fractions from becoming overheated in the early stages of contact with the heat carrier as the materials enter the zone of the maximum temperature.
A method of heating coal is also known, in which, in order to regulate the thermal conditions in the zone of maximum heat of the heat carrier, a separate stream of heat carrier is introduced into such zone and subsequently released into the atmosphere.
The above method is performed in an apparatus comprising a means for producing a heat carrier and a plurality of heaters having a feed tube for supplying the materials to be heated and the heat carrier, a means adapted to separate the heated materials from waste heat carrier, a tube for discharge of heat carrier and a tube for discharge of heated materials, both connected to the separating means, the last heating zone having an additional means for producing a heat carrier with a higher temperature than that of the heat carrier provided by the preceding heating zone.
The disadvantages of the above method include release of high-temperature waste heat carrier into the atmosphere, and lack of provision for regulating heat distribution between the heat-treatment zones.
A disadvantage common to all of the above methods, consists in the inability to intensify the heat-treatment of the materials in the early heating zones, and consequently in the time-consuming process.
The apparatus of the prior art suffer from a common disadvantage of an inefficient distribution of heat between the heaters with consequent non-uniform heating of the smaller coal fractions, as well as a limited capacity and low efficiency of the installations.